This
book, with 400,000 copies in print just two months after its
publication, has created an enormous stir. The authors
unabashedly assert that scientific evidence demonstrates the
existence of genetically based differences in intelligence
among social classes and races. They maintain further that
data from some 1,000 publications in the social and
biological sciences show that attributes such as employment,
income, welfare dependency, divorce and quality of parental
behavior are determined by an individual's intelligence.
These claims--another eruption of the crude biological
determinism that permeates the history of IQ testing--lead
Herrnstein and Murray to a number of social policy
recommendations. The policies would not be necessary, or
humane, even if the cited evidence were valid. But the
caliber of the data in "The Bell Curve" is, at many
critical points, pathetic. Further, the authors repeatedly
fail to distinguish between correlation and causation and
thus draw many inappropriate conclusions.

I will
deal first with an especially troubling example of the
quality of the data on which Herrnstein and Murray rely. They
ask, "How do African-Americans compare with blacks in
Africa on cognitive tests?" They reason that low
African-American IQ scores might be the result either of a
history of slavery and discrimination or of genetic factors.
Herrnstein and Murray evidently assume that blacks reared in
colonial Africa have not been subjected to discrimination. In
their view, if low IQ scores of African-Americans are a
product of discrimination, rather than genes, black Africans
should have higher IQs than African-Americans.

To
answer the question they have posed, Herrnstein and Murray
call on the authority of Richard Lynn of the University of
Ulster in Ireland, described as "a leading scholar of
racial and ethnic differences," from whose advice they
have "benefited especially." They state that Lynn,
who in 1991 reviewed 11 African IQ studies, "estimated
the median black African IQ to be 75...about 10 points lower
than the current figure for American blacks." Herrnstein
and Murray conclude that the "special
circumstances" of African-Americans cannot explain their
low average IQ relative to whites. That leaves genetics free
to explain the black-white difference.

But why
do black Americans have higher scores than black Africans?
Herrnstein and Murray, citing "Owen 1992," write
that "the IQ of 'coloured' students in South Africa--of
mixed racial background--has been found to be similar to that
of American blacks." The implication is clear: the
admixture of Caucasian and African genes, both in South
Africa and in the U.S., boosts "coloured" IQ 10
points above that of native Africans. But the claims made
regarding African and coloured IQs cannot withstand critical
scrutiny.

Lynn's
1991 paper describes a 1989 publication by Ken Owen as
"the best single study of the Negroid
intelligence." The study compared white, Indian and
black pupils on the Junior Aptitude Tests; no coloured pupils
were included. The mean "Negroid" IQ in that study,
according to Lynn, was 69. But Owen did not in fact assign
IQs to any of the groups he tested; he merely reported
test-score differences between groups, expressed in terms of
standard deviation units. The IQ figure was concocted by Lynn
out of those data. There is, as Owen made clear, no reason to
suppose that low scores of blacks had much to do with
genetics: "the knowledge of English of the majority of
black testees was so poor that certain [of the]
tests...proved to be virtually unusable." Further, the
tests assumed that Zulu pupils were familiar with electrical
appliances, microscopes and "Western type of ladies'
accessories."

In 1992
Owen reported on a sample of coloured students that had been
added to the groups he had tested earlier. The footnote in
"The Bell Curve" seems to credit this report as
proving that South African coloured students have an IQ
"similar to that of American blacks," that is,
about 85 (the actual reference does not appear in the book's
bibliography). That statement does not correctly characterize
Owen's work. The test used by Owen in 1992 was the
"nonverbal" Raven's Progressive Matrices, which is
thought to be less culturally biased than other IQ tests. He
was able to compare the performance of coloured students with
that of the whites, blacks and Indians in his 1989 study
because the earlier set of pupils had taken the Progressive
Matrices in addition to the Junior Aptitude Tests. The black
pupils, recall, had poor knowledge of English, but Owen felt
that the instructions for the Matrices "are so easy that
they can be explained with gestures."

Owen's
1992 paper again does not assign IQs to the pupils. Rather he
gives the mean number of correct responses on the Progressive
Matrices (out of a possible 60) for each group: 45 for
whites, 42 for Indians, 37 for coloureds and 28 for blacks.
The test's developer, John Raven, repeatedly insisted that
results on the Progressive Matrices tests cannot be converted
into IQs. Matrices scores, unlike IQs, are not symmetrical
around their mean (no "bell curve" here). There is
thus no meaningful way to convert an average of raw Matrices
scores into an IQ, and no comparison with American black IQs
is possible.

The
remaining studies cited by Lynn, and accepted as valid by
Herrnstein and Murray, tell us little about African
intelligence but do tell us something about Lynn's
scholarship. One of the 11 entries in Lynn's table of the
intelligence of "pure Negroids" indicates that
1,011 Zambians who were given the Progressive Matrices had a
lamentably low average IQ of 75. The source for this
quantitative claim is given as "Pons 1974; Crawford-Nutt
1976."

A. L.
Pons did test 1,011 Zambian copper miners, whose average
number of correct responses was 34. Pons reported on this
work orally; his data were summarized in tabular form in a
paper by D. H. Crawford-Nutt. Lynn took the Pons data from
Crawford-Nutt's paper and converted the number of correct
responses into a bogus average "IQ" of 75. Lynn
chose to ignore the substance of Crawford-Nutt's paper, which
reported that 228 black high school students in Soweto scored
an average of 45 correct responses on the Matrices--HIGHER
than the mean of 44 achieved by the same-age white sample on
whom the test's norms had been established and well above the
mean of Owen's coloured pupils.

Seven of
the 11 studies selected by Lynn for inclusion in his
"Negroid" table reported only average Matrices
scores, not IQs; the other studies used tests clearly
dependent on cultural content. Lynn had earlier, in a 1978
paper, summarized six studies of African pupils, most using
the Matrices. The arbitrary IQs concocted by Lynn for those
studies ranged between 75 and 88, with a median of 84. Five
of those six studies were omitted from Lynn's 1991 summary,
by which time African IQ had, in his judgment, plummeted to
69.

Lynn's
distortions and misrepresentations of the data constitute a
truly venomous racism, combined with scandalous disregard for
scientific objectivity. Lynn is widely known among academics
to be an associate editor of the racist journal "Mankind
Quarterly" and a major recipient of financial support
from the nativist, eugenically oriented Pioneer Fund. It is a
matter of shame and disgrace that two eminent social
scientists, fully aware of the sensitivity of the issues they
address, take Lynn as their scientific tutor and uncritically
accept his surveys of research.

I turn
now to a revealing example of Herrnstein and Murray's
tendency to ignore the difference between mere statistical
associations (correlations) and cause-and-effect
relationships. The authors lament that "private
complaints about the incompetent affirmative-action hiree are
much more common than scholarly examination of the
issue." They then proceed to a scholarly and public
discussion of "teacher competency examinations."
They report that such exams have had "generally
beneficial effects," presumably by weeding out
incompetent affirmative-action hirees. That view of tests for
teachers is not shared by those who argue that because blacks
tend to get lower scores, the tests are a way of eliminating
competent black teachers. But Herrnstein and Murray assure us
that "teachers who score higher on the tests have
greater success with their students."

To
support that statement, they cite a single study by two
economists who analyzed data from a large number of North
Carolina school districts. The researchers obtained average
teacher test scores (a measure of "teacher
quality") and pupil failure rates for each district.
They reported that a "1% increase in teacher
quality...is accompanied by a 5% decline in the...rate of
failure of students"--that is, there were fewer student
failures in districts where teachers had higher test scores.
It does not follow from such a correlation, however, that
hiring teachers with higher test scores will reduce the rate
of student failure. The same researchers found, to their
surprise, that "larger class size tends to lead to
improved average [pupil] performance." Does it follow
that increasing the pupil-to-teacher ratio would further
improve student performance? That policy might please many
taxpayers, just as firing teachers with lower test scores
would please some. But neither policy derives logically from
the observed correlations.

To
understand why, consider the following. The average
proportion of black students across the North Carolina school
districts was 31 percent. Suppose--it does not stretch
credulity--that black teachers (who have lower test scores)
tend to work in districts with large proportions of black
pupils (who have higher failure rates). Such nonrandom
assignment of teachers would produce a correlation between
teacher test scores and pupil failure rates, but one cannot
then conclude that the teachers' test scores have any causal
relation to student failure. To argue that, one would have to
show that for a group of black teachers and for a separate
group of white teachers, teachers' test scores predicted the
failure rates of their students. No such information was
available to the original researchers or to Herrnstein and
Murray.

What
about the finding that high pupil-to-teacher ratios are
associated with good pupil performance? There is no way to be
certain, but suppose deprived black children tended to be in
small, de facto segregated rural schools, whereas more
privileged whites were in larger classrooms. Would cramming
more pupils into the rural schools promote academic
excellence?

There is
an important and general lesson buried in this example: the
arithmetical complexity of the multitude of correlations and
logistic regressions stuffed into "The Bell Curve"
does not elevate their status from mere associations to
causes and effects.

The
confusion between correlation and causation permeates the
book's largest section, which consists of an interminable
series of analyses of data taken from the National
Longitudinal Survey of Labor Market Experience of Youth
(NLSY). Those data, not surprisingly, indicate that there is
an association within each race between IQ and socioeconomic
status. Herrnstein and Murray labor mightily to show that low
IQ is the cause of low socioeconomic status, and not vice
versa. The argument is decked out in all the trappings of
science--a veritable barrage of charts, graphs, tables,
appendices and appeals to statistical techniques that are
unknown to many readers. But on close examination, this
scientific emperor is wearing no clothes.

The NLSY
survey included more than 12,000 youngsters, who were aged 14
to 22 when the continuing study began in 1979. At that time
the respondents or their parents gave information about their
educations, occupations and incomes and answered questions
about themselves. Those reports are the basis for classifying
the childhood socioeconomic status of the respondents. The
teenagers also took the Armed Forces Qualification Test,
regarded by psychometricians as essentially an IQ test. As
they have grown older, the respondents have provided more
information about their own schooling, unemployment, poverty,
marital status, childbearing, welfare dependency,
criminality, parenting behavior and so on.

Herrnstein
and Murray pick over these data, trying to show that it is
overwhelmingly IQ--not childhood or adult socioeconomic
status--that determines worldly success and the moral
praiseworthiness of one's social behaviors. But their
dismissal of socioeconomic status rests ultimately on the
self-reports of youngsters, which do not form an entirely
firm basis.

I do not
suggest that such self-reports are entirely unrelated to
reality. We know from many sources that children from
differing social class backgrounds do indeed differ in
measured IQ. And in the NLSY study, after all, the
respondents' self-reports are correlated with the objective
facts of their IQ scores. But comparing the predictive value
of those self-reports with that of test scores is playing
with loaded dice.

Further,
the fact that self-reports are correlated with IQ scores is,
like all correlations, ambiguous. For Herrnstein and Murray,
the relation of their index of parental socioeconomic status
to the child's IQ means that parents of high status--the
"cream floating on the surface of American
society"--have transmitted high-quality genes to their
offspring. But other interpretations are possible. Perhaps
the kinds of people who get high test scores are precisely
those who are vain enough to claim exaggerated social status
for themselves. That tendency could artificially inflate
correlations of IQ both with parental socioeconomic status
and with self-reports of success, distorting all tests of the
relative predictive power of socio-economic status and IQ.
Such an explanation may seem far-fetched to some readers, but
it is clearly a logical possibility. The choice between such
alternative interpretations of statistical associations
cannot be based on logic alone. There is plenty of elbow room
for ideological bias in social science.

The core
of the Herrnstein-Murray message is phrased with a beguiling
simplicity: "Putting it all together, success and
failure in the American economy, and all that goes with it,
are increasingly a matter of the genes that people
inherit." Income is a "family trait" because
IQ, "a major predictor of income, passes on sufficiently
from one generation to the next to constrain economic
mobility." Those at the bottom of the economic heap were
unlucky when the genes were passed out, and they will remain
there.

The
correlations with which Herrnstein and Murray are obsessed
are of course real: the children of day laborers are less
likely than the children of stockbrokers to acquire fortunes
or to go to college. They are more likely to be delinquent,
to receive welfare, to have children outside of marriage, to
be unemployed and to have low-birth-weight babies. The
children of laborers have lower average IQs than do the
children of brokers, and so IQ is also related to all these
phenomena. Herrnstein and Murray's intent is to convince us
that low IQ causes poverty and its attendant evils--not, as
others hold, vice versa.

For
eight dense chapters, the authors of "The Bell
Curve" wrestle with data from the NLSY survey,
attempting to disentangle the roles of IQ and of
socioeconomic status. They employ a number of quantitative
tools, most prominently logistic regression, a technique that
purports to specify what would happen if one variable were
"held constant" while another variable were left
free to vary. When socioeconomic status is statistically held
constant by Herrnstein and Murray, IQ remains related to all
the phenomena described. When IQ is held constant, the effect
of socioeconomic status is invariably reduced, usually
substantially, and sometimes eliminated.

There
are a number of criticisms to be made regarding the ways in
which Herrnstein and Murray analyze these data. But for
argument's sake, let us suppose that their analyses are
appropriate and accurate. We can also grant that, rightly or
wrongly, disproportionate salaries and wealth accrue to those
with high IQ scores. What then do the Herrnstein-Murray
analyses tell us?

The
socioeconomic status of one's parents cannot in any immediate
sense "cause" one's IQ to be high or low. Family
income obviously cannot directly determine a child's
performance on an IQ test. But income and the other
components of an index of socioeconomic status can serve as
rough indicators of the rearing environment to which a child
has been exposed. With exceptions, a child of a well-to-do
broker is more likely to be exposed to book learning earlier
and more intensively than is a child of a laborer. And
extensive practice at reading and calculating does affect,
very directly, one's IQ score. That is one plausible way of
interpreting the statistical link between parental
socioeconomic status and a child's IQ.

The
significant question is not whether socioeconomic status, as
defined by Herrnstein and Murray, is more or less
statistically associated with success than is their measure
of IQ. Different measures of socioeconomic status, or
different IQ tests, might substantially affect the results
they obtained; other scholars, using other indices and tests,
have in fact achieved quite different results. The
significant question is, why don't the children of laborers
acquire the skills that are tapped by IQ tests?

Herrnstein
and Murray answer that the children of the poor, like their
laborer parents before them, have been born with poor genes.
Armed with that conviction, the authors hail as "a great
American success story" that after "controlling for
IQ," ethnic and racial discrepancies in education, wages
and so forth are "strikingly diminished." They
reach this happy conclusion on the questionable basis of
their regression analyses. But the data, even if true, allow
another reading. We can view it as a tragic failure of
American society that so few black and low-socioeconomic
status children are lucky enough to be reared in environments
that nurture the skills needed to obtain high IQ scores. For
Herrnstein and Murray, it is only fair that the race should
go to the swift, who are blessed with good genes and high
IQs. The conception that our society hobbles most of the
contestants at the starting line does not occur to them.

In the
world of "The Bell Curve," the explanatory power of
IQ is ubiquitous. The authors note that among blue-collar
workers who tell researchers that they have dropped out of
the labor force because of physical disability or injury, low
IQ is common. Why? "An answer leaps to mind: The smarter
you are, the less likely that you will have accidents."
That answer leapt to mind before the thought that low-IQ
workers, in minimum wage jobs, have little incentive to
remain in the labor force. Dull young women lack the
"foresight and intelligence" to understand that the
welfare system offers them a bad deal. Welfare might be a bad
deal for Herrnstein and Murray, but I am not so sure that
single mothers on welfare have not figured out THEIR odds
pretty accurately.

People
who have low IQs, according to "The Bell Curve,"
commit crimes because they lack foresight, and so the threat
of prison does not deter them. Further, they cannot
"understand why robbing someone is wrong." Then
what is to be made of the fact that although "very
dull" young males are stopped by the police, booked for
an offense and convicted less often than "normal"
males, they are nevertheless jailed more than twice as often?
"It may be...that they are less competent in getting
favorable treatment from the criminal justice system. The
data give us no way to tell." Perhaps not, but some
hints are available. There is no doubt that O. J. Simpson is
"competent," but his ability to hire high-priced
lawyers is not irrelevant to the treatment he will receive
from the criminal justice system.

"The
Bell Curve," near its closing tail, contains two
chapters concerned with affirmative action, both in higher
education and in the workplace. To read those chapters is to
hear the second shoe drop. The rest of the book, I believe,
was written merely as a prelude to its assault on affirmative
action. The vigor of the attack is astonishing.

Affirmative
action "cannot survive public scrutiny." It is
based on "the explicit assumption that ethnic groups do
not differ in...abilities." Hiring and promotion
procedures "that are truly fair...will produce...racial
disparities," and "employers are using dual
standards for black and white job applicants because someone
or something...is making them do so." That behavior has
resulted in the "degradation of intellectual
requirements" in recruiting police, which has affected
"police performance on the street." We learn that a
veteran of the Washington, D.C., police force has heard
"about people in the academy who could not read or
write." And a former instructor saw "people
diagnosed as borderline retarded graduate from the police
academy." These anecdotes take their place among the
politically potent folktales about welfare queens driving
Cadillacs.

At long
last, Herrnstein and Murray let it all hang out:
"Affirmative action, in education and the workplace
alike, is leaking a poison into the American soul."
Having examined the American condition at the close of the
20th century, these two philosopher-kings conclude, "It
is time for America once again to try living with inequality,
as life is lived...." This kind of sentiment, I imagine,
is what led "New York Times" columnist Bob Herbert
to the conclusion that "The Bell Curve" "is
just a genteel way of calling somebody a nigger."
Herbert is right. The book has nothing to do with science.

LEON J.
KAMIN is professor of psychology at Northeastern University
in Boston. His more extensive critique of this work will
appear in "The Bell Curve Debate," edited by
Russell Jacoby and Naomi Glauberman (Times Books/Random
House, 1995).

SCIENTIFIC
AMERICAN February 1995 Volume 272 Number 2 Pages 99-103

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